X
experimental, reactance, unknown quantity, ordinate, experimental    X
without interest     x –in. or
x - int
expendable bathythermograph    XBT
without dividend     xd. Or x-div.
(Chem.) xenon     Xe
extra-fast patrol boat    XFPB
extra large     XL
experimental mobile-launched surface attack guided missile designator (USA)    XMGM
Christian     Xn.
Christianity    Xnty.
without rights     xr.
(Radio.) atmospherics     Xs
expendable sound velocity system    XSV
Christ     Xt.